Biliopancreatic diversion (BPD) has made reacceptable the malabsorptive approach to the surgical treatment of obesity. The procedure, in a series of 2273 patients operated on during a 21 years period, caused a mean permanent reduction of about 75% of the initial excess weight. The indefinite weight maintenance appears to be due to the existence of a threshold absorption capacity for fat and starch, and thus energy, while the weight loss is partly due to increased resting energy expenditure. Other beneficial effects, besides those consequent to weight loss and/or reduced nutrient absorption, included permanent normalization of serum glucose and cholesterol without any medication and on totally free diet in 100% of cases, both phenomena being due to a specific action of the operation. Operative mortality was less than 0.5%. Specific late complications included: anemia, less than 5% with adequate iron and/or folate supplementations; stomal ulcer, reduced to 3.0% by oral H-2-blockers prophylaxis; bone demineralization, increasing up to the fourth year and tending to decrease thereafter, with need of calcium and vitamin D supplementation: neurological complications, totally avoidable by prompt vitamin B administration to patients at risk, protein malnutrition, which was reduced to a minimum of 2.8% with 1.2% recurrence, in exchange with a smaller weight loss. by adapting the volume of the gastric remnant and the length of the alimentary limb to the patient's individual characteristics. It is concluded that the correct use of BPD, based on the knowledge of its mechanisms of action, can make the procedure a very effective and safe one in all hands.

Background: The continuing evolution and the mechanisms of actions of biliopancreatic diversion (BPD) as malabsorptive approach to the surgical treatment of obesity are evaluated.

Small bowel obstruction occurred in nine of 880 patients undergoing biliopancreatic diversion. This complication has different features depending on the site of the obstruction. Obstruction of the alimentary limb is mainly characterized by vomiting, is easy to diagnose, and is not catastrophic. When the common limb is affected, the pattern is similar to that of a low small bowel obstruction in an intact intestine. The most dangerous event is obstruction of the biliopancreatic limb because symptoms are unclear and often misleading, and standard radiology is useless. The possibility of the ensuing diagnosis being wrong or delayed can contribute to potentially lethal complications, namely perforation and acute pancreatitis. Serum amylase level determination and an abdominal ultrasound scan are essential for prompt diagnosis.

The body composition of lean control subjects was compared with that of subjects following biliopancreatic diversion for morbid obesity, when their excess weight had been stabilized at under 40 per cent of the ideal body weight value for over two years. Lean body mass, body cell mass and fat were indirectly calculated from total body water and total body sodium, measured by isotope dilution technique. The body composition in the two groups of subjects was essentially normal, as was indicated by the percentage values of the body composition parameters and by the linear correlations between body weight and the lean body compartments size.

The nutritional status prior to and 3 months and 1 year after biliopancreatic bypass surgery was evaluated. The common nutritional indexes (serum albumin and transferin concentrations, daily urinary creatinine excretion and delayed hypersensitivity) were determined. The body compartments were derived from total body water (TBW) and total body sodium (TBNa), measured by dilutional technique, and total body potassium (TBK), calculated from TBW, TBNa, and the ratio of the sodium plus potassium content divided by the water content in a sample of whole blood. Before surgery, obese patients showed a dilatation of both fat an lean compartments with a normal lean body mass (LBM) qualitative composition, as indicated by TBNa/TBW, and TBNa/TBK ratios not greater than those measured in controls. Three months following very-little-stomach biliopancreatic bypass (VLS BPB), a consistent reduction of body weight and body fat were observed. The body cell mass value fell and reached a level closely similar to that found in lean control subjects. LBM showed only a slight decrease. A sharp increase of TBNa/TBW and TBNa/TBK ratios demonstrated a dilatation of the extracellular space. This malnutritional status was not detected by the usual nutritional parameters. One year after VLS BPB surgery, the patients' body composition became very similar to that of lean subjects, though a TBNa greater than that of controls suggested that a slightly expanded extracellular space was still present.

Biliopancreatic diversion is a very effective method for weight reduction. In some instances it is too effective and needs to be revised.

Protein malnutrition is the main early problem with biliopancreatic diversion; gastric volume greatly influences the incidence of protein malnutrition.